Neutrino masses from low scale partial compositeness

We consider a class of models in which the neutrinos acquire Majorana masses through mixing with singlet neutrinos that emerge as composite states of a strongly coupled hidden sector. In this framework, the light neutrinos are partially composite particles that obtain their masses through the inverse seesaw mechanism. We focus on the scenario in which the strong dynamics is approximately conformal in the ultraviolet, and the compositeness scale lies at or below the weak scale. The small parameters in the Lagrangian necessary to realize the observed neutrino masses can naturally arise as a consequence of the scaling dimensions of operators in the conformal field theory. We show that this class of models has interesting implications for a wide variety of experiments, including colliders and beam dumps, searches for lepton flavor violation and neutrinoless double beta decay, and cosmological observations. At colliders and beam dumps, this scenario can give rise to striking signals involving multiple displaced vertices. The exchange of hidden sector states can lead to observable rates for flavor violating processes such as μ → eγ and μ → e conversion. If the compositeness scale lies at or below a hundred MeV, the rate for neutrinoless double beta decay is suppressed by form factors and may be reduced by an order of magnitude or more. The late decays of relic singlet neutrinos can give rise to spectral distortions in the cosmic microwave background that are large enough to be observed in future experiments.

Pseudoscalar pair production via off-shell Higgs in composite Higgs models

We propose a new type of search for a pseudoscalar particle \etaη pair produced via an off-shell Higgs, pp\to h^*\to \eta\etapp→h*→ηη. The search is motivated by a composite Higgs model in which the \etaη is extremely narrow and decays almost exclusively into Z\gammaZγ in the mass range 65{\mathrm{GeV}}\lesssim m_\eta \lesssim 160{\mathrm{GeV}}65GeV≲mη≲160GeV. We devise an analysis strategy to observe the novel Z\gamma Z\gammaZγZγ channel and estimate potential bounds on the Higgs-\etaη coupling. The experimental sensitivity to the signatures depends on the power to identify fake photons and on the ability to predict large photon multiplicities. This search allows us to exclude large values of the compositeness scale ff, being thus complementary to other typical processes.

Sigma-assisted low scale composite Goldstone–Higgs

We show that the presence of a lightish scalar resonance, $$\sigma $$σ, that mixes with the composite Goldstone–Higgs boson can relax the typical bounds found in this class of models. This mechanism, inbred in models with a walking dynamics above the condensation scale, allows for a low compositeness scale $$f \gtrsim 400$$f≳400 GeV, corresponding to a misalignment angle $$s_\theta \lesssim 0.6$$sθ≲0.6, contrary to the common lore of a smaller angle. According to recent lattice results, the light $$\sigma $$σ emerges thanks to a near-conformal phase above the condensation scale, consistent to the requirements from flavour physics. We study this effect in a general way, showing that it appears in all cosets emerging from an underlying gauge-fermion dynamics, in the presence of top partial compositeness. The scenario is testable both on the Lattice and experimentally, as it requires the presence of a second broad Higgs-like resonance, below 1 TeV, that can be revealed at the LHC in the ZZ and $$t\bar{t}$$tt¯ channels.

Excited quarks production at FCC and SppC pp colliders

Potential discovery, observation and exclusion limits of excited [Formula: see text] and [Formula: see text] quarks with gamma[Formula: see text]jet final state are researched at the multi-TeV scale colliders, FCC and S[Formula: see text]C in this paper. Both colliders, FCC and S[Formula: see text]C, show that excited [Formula: see text] and [Formula: see text] quarks could be discovered up to 42.1 TeV and 55.2 TeV for [Formula: see text], 30.3 TeV and 39.4 TeV for [Formula: see text] and 42.3 TeV and 55.5 TeV mass values for degenerate case [Formula: see text], respectively. The determination of the excited quarks compositeness scale is examined, which will be up to multi-PeV level. Besides these analyses, free parameters ([Formula: see text], [Formula: see text] and [Formula: see text]) are scanned from around 0.1 up to 1 that show excited quark could be discovered at dozens of TeV with even coupling constants under 0.1.

Search for Excited u and d Quarks in Dijet Final States at Future pp Colliders

Resonant production of excited u and d quarks at the Future Circular Collider and Super Proton-Proton Collider has been researched. Dominant jet-jet decay mode has been considered. It is shown that FCC and SppC have great potential for discovery of excited u (d) quark: up to 44.1 (36.3) and 58.4 (47.8) TeV masses, respectively. For degenerate case (Mu⋆ = Md⋆), these values are 45.9 and 60.9 TeV, respectively. This discovery will also afford an opportunity to determine the compositeness scale up to multi-PeV level.

Search for Compositeness in Dilepton Final States at DØ

We report preliminary results of a search for substructure in quarks and leptons assuming a four-fermion contact interaction for dielectron pairs of large invariant mass. The search is based on dielectron data collected by the DØ detector in [Formula: see text] collisions at [Formula: see text]. The results agree well with predictions of the standard model and we obtain model-dependent lower limits at 95% confidence level on the compositeness scale of 3.6 to 9.1 TeV for different chiral models of the composite structure of quarks and electrons.

HIGGS PROPAGATOR IN THE PRESENCE OF STRONG DYNAMICS IN THE ELECTROWEAK SECTOR

The Higgs propagator, in the presence of strong top-Yukawa coupling, is expressed in the form of dispersion integrals so that unitarity in top–antitop scattering amplitude is maintained. It is found that a large top-Yukawa coupling lowers the Higgs mass from the condensate-model value of twice the top mass (≈350 GeV) to 100–200 GeV consistent with the Z0 width precision measurements. The coupling is found to be ≈3.7 at the top-mass, much larger than the Standard Model value ≈1. It corresponds to a compositeness scale ≈1.4 TeV, which is consistent with top-color models. A second scalar state around 1 TeV also emerges as a solution in combination with the low mass Higgs.

TESTING VECTOR BOSON DOMINANCE OF ELECTROWEAK INTERACTIONS VIA e+e− ANNIHILATION INTO BOSON PAIRS

In the framework of the unified compositeness of leptons, quarks and Higgs bosons, supplemented with the hypothesis of the vector boson dominance of the SM gauge interactions, restrictions on the universal residual fermion–boson and boson–boson interactionsare investigated. Manifestations of the universal interactions in the W+W− and ZH boson pair production at the 2 TeV e+e− linear collider are studied. Definite signaturesof these interactions are exposed, and their relations to the nonstandard triple gaugeinteractions are considered. It is shown that the unified substructure could be tested atthe collider in these processes up to the compositeness scale [Formula: see text], which liesin the naturally preferred deca-TeV region. Importance of the optimal angular cutoffsand the polarized beams is found.

UNIVERSAL PARAMETRIZATION FOR QUARK AND LEPTON SUBSTRUCTURE

A universal parametrization for possible quark and lepton substructure is advocated in terms of quark and lepton form factors. It is emphasized that the lower bounds on compositeness scale, Λc, to be determined experimentally depend strongly on their definitions in composite models. From the recent HERA data, it is estimated to be Λc>50 GeV , 0.4 TeV and 10 TeV, depending on the parametrizations with a single-pole form factor, a contact interaction and a logarithmic form factor, respectively.